User manual

Chapter 3 Software Overview
© National Instruments Corporation 3-17 NI-DAQ User Manual for PC Compatibles
AI_Mux_Config
Configures the number of multiplexer
(AMUX-64T) devices connected to
an MIO and AI device and informs
NI-DAQ if any AMUX-64T devices are
attached to the system. This function
applies only to the MIO and AI devices.
AI_Read
Reads an analog input channel (initiates
anA/Dconversiononananaloginput
channel) and returns the unscaled result.
AI_Read_Scan
Returns readings for all analog input
channels selected by
Scan_Setup
.
AI_Read_VScan
Returns readings in volts for analog input
channels selected by
Scan_Setup
.
AI_Setup
Selects the specified analog input channel
and gain setting for externally pulsed
conversion operations.
AI_VRead
Reads an analog input channel (initiates
anA/Dconversiononananaloginput
channel) and returns the result scaled
to a voltage in units of volts.
AI_VScale
Converts the binary result from an
AI_Read
call to the actual input voltage.
Single-Channel Analog Input Application Tips
All of the NI-DAQ functions described in this section are for nonbuffered
single-point analog input readings. For buffered data acquisition, consult
the Data Acquisition Functions section later in this chapter.
Two of the
AI
functions are related to device configuration. If you
have changed the device jumper settings from the factory-default settings
or want to reprogram the E Series devices, call
AI_Configure
at the
beginning of your application to inform NI-DAQ about the changes.
Furthermore, if you have connected multiplexer devices (AMUX-64T) to
your MIO and AI devices, call
AI_Mux_Config
once at the beginning of
your application to inform NI-DAQ about the multiplexer devices.
For most purposes,
AI_VRead
is the only function required to perform
single-point analog input readings. Use
AI_Read
when unscaled data is
sufficient or when extra time taken by
AI_VRead
to scale the data is